Vehicles may have a hydraulic clutch actuation system with a master cylinder 1 and a slave cylinder 2, as illustrated in FIG. 1, which is a replica of FIG. 1 from U.S. Pat. No. 6,742,643 B2.
When a driver activates a clutch pedal 3, a rod 4 causes a master piston to move into the master cylinder 1, which causes a hydraulic fluid to flow in a hydraulic line 5 towards the slave cylinder 2, where a slave piston moves a second rod 6 outward, which is connected to a lever 7 to engage or disengage a clutch from a flywheel 8, which is connected to a crank 9 of a combustion engine.
Vibrations of the engine (e.g. axial vibrations on the crank 9) are transmitted all the way back via the flywheel 8, lever 7, rod 6, slave cylinder 2, hydraulic line 5, master cylinder 1, rod 4 to the clutch pedal 3, where it may be perceptible by the driver and may even cause acoustic noise. The fluid as well as the tubing can act as transformers for vibrations, which are perceptible at the clutch pedal by the driver.
Several damping devices (also known as “vibration cancellers” or “vibration absorbers”) applicable to clutch release systems are described in the art.
DE 10 2009 049 243 A1 discloses a vibration absorber, particularly a hydraulic vibration absorber, for a hydraulic actuation system of a motor vehicle clutch, which has a housing whose internal space is connected with a hydraulic cable of a hydraulic actuation system.
WO 2008/086777 A1 discloses an apparatus for suppressing natural resonances in a hydraulic path which actuates a clutch, wherein a pressure line produces a connection between a master cylinder and a slave cylinder and the apparatus, as a branch line, encloses a fluid column. The frequency of the fluid column can be tuned to the excitation frequency of each drive motor used in the system. The volume of the fluid column acts as a medium for the de-excitation frequency and can be varied by changing the length of the enclosure of the fluid column.
U.S. Pat. No. 7,350,354 B2 discloses a hydraulic actuation apparatus for a motor vehicle clutch, including a master cylinder, a slave cylinder, a hydraulic line connecting the master cylinder to the slave cylinder to form a pressure space, and a damping member arranged in the pressure space for attenuating pressure pulses. The damping member includes a connection channel connected to the main fluid channel and a fluid guide directing fluid from the main fluid channel into the connection channel.
U.S. Pat. No. 6,742,643 B2 discloses a damper for provision in a hydraulic actuator system between the master cylinder and a slave cylinder of the system. The damper includes a housing including a damper port for connection in the system and a diaphragm carried by the housing and co-acting with the housing to define a chamber above the diaphragm and in communication with the damper port so that the diaphragm may deflect in response to vibrations transmitted through the hydraulic fluid in the system to effect damping of the vibrations.
U.S. Pat. No. 5,070,983 discloses a damper which is adapted for installation in a clutch hydraulic actuator system between the master cylinder and slave cylinder and includes a housing, a diaphragm mounted in the housing with its periphery fixed with respect to the housing and having a first face constituting a boundary wall of the hydraulic system so that the diaphragm deflects in response to vibrations transmitted through hydraulic fluid in the system to effect damping of the vibrations.
US 2002/0129603 A1 discloses a device to reduce vibrations in a hydraulic force transfer system which has a master cylinder and a slave cylinder connected with this via a fluid column. The device has a housing and a membrane attached by its edge to the housing. The membrane is pressed, at least in the rest state of the hydraulic force transfer system, by means of a spring element against the direction of the hydraulic pressure on the membrane against a chamber-side support surface.
KR 20130116390 describes an anti-vibration device for a vehicle clutch pedal. The anti-vibration device includes: a valve piston which blocks a flow path while the clutch pedal is in a paused state; and a rubber dynamic damper connected to an oil operation path. Accordingly, the anti-vibration device can reduce the vibration generated during a dynamic state when the clutch pedal is operated and during a static state when the clutch pedal is paused.
KR 1020080051521 A is related to a damper pipe for absorbing vibration of a clutch pedal. To reduce an installation cost and to damp different frequencies of vibration a corrugated damping unit is installed in a hydraulic pipe.
US 2014/0353098 A1 discloses a selectively fixed damper. A lockable damper includes moving a valve assembly together with a piston assembly between a retracted position and extended position relative to a tube, the moving unassisted by the lockable damper.
US 2002/0129603 A1 discloses a device to reduce vibrations in a hydraulic force transfer system. The device has a housing and the membrane delimits a chamber which can be connected via a connection with a master cylinder and via a further connection with a slave cylinder so that the membrane can be hydraulically pressurized by the fluid column between the master cylinder and slave cylinder.
However, the inventors herein have recognized that the vibration dampers described above do not provide damping at more than one resonance frequency. Furthermore, the damping characteristic provided by the vibration damper described in the references above are fixed by design, meaning that the damping behavior of the damper is not user-adjustable.
The inventors herein have recognized the above cited potential issues, and provide systems and methods to at least partially address the issues. In one example, a vibration damper for a hydraulic clutch actuator system includes a rigid housing comprising a chamber, an inlet port and an outlet port and a channel fluidly connecting the inlet port and the outlet port, and a propeller comprising a plurality of blades. The propeller is rotatably mounted in said chamber and the chamber is fluidly connected with the channel in such a way that movement of fluid through the channel causes rotation of the propeller. The vibration damper further includes a spiral torsion spring operatively connected to said propeller in such a way that rotation of the propeller causes winding or unwinding of the spring.
In this way, the vibration damper may reduce vibration by absorbing high frequency vibration energy through the drag force applied by the fluid movement to the propeller blades and absorbing low frequency vibration through the winding and/or unwinding of the torsional spring. Further, by designing a vibration damper which can dampen one or more resonance frequencies, the vibration experienced during different driving conditions may be reduced which further improves the customer's driving comfort. By absorbing the undesired engine vibrations effectively, engine performance may be increased, which may further lead to improved fuel economy and overall increase in engine efficiency.
Thus, the vibration damper presented herein may easily be fine-tuned, not only at design-time, but also after installation, in particular without having to remove the damping device from the hydraulic system.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.